Image display device and display apparatus

ABSTRACT

An image display device including: an image formation device; and an optical system that brings an image from the image formation device to an eyeball of an observer. 0 (degrees)≤ω 2 &lt;ω 1 ≤25 is satisfied where an image-formation-device first strike point is where an extended line of an optical axis of the optical system intersects with an image exit surface of the image formation device, a first normal line is normal to the image exit surface of the image formation device passing through the first strike point, an image-formation-device second strike point is where an extended line of a pupil center line of the eyeball of the observer intersects with the image exit surface of the image formation device, a second normal line is normal to the image exit surface of the image formation device passing through the second strike point.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International PatentApplication No. PCT/JP2015/064925 filed on May 25, 2015, which claimspriority benefit of Japanese Patent Application No. JP 2014-165735 filedin the Japan Patent Office on Aug. 18, 2014. Each of theabove-referenced applications is hereby incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present disclosure relates to image display devices and displayapparatuses. More particularly, the present disclosure relates to adisplay apparatus which can be used as, for example, a head mounteddisplay (HMD), and an image display device which is suitably used insuch a display apparatus.

BACKGROUND ART

A virtual-image display apparatus (display apparatus) which enables anobserver to observe a two-dimensional image formed using an imageformation device as a magnified virtual image, using a virtual-imageoptical system, is well known, as disclosed in JP H05-134208A. In adisplay apparatus disclosed in JP H05-134208A, a liquid crystal displayunit is illuminated with light from a light source which has beencollimated by a lens, through a polarizing plate, image light of theilluminated liquid crystal display unit is brought into a first focalpoint by lens group, and the focused light is reflected by a concavemirror, is brought into a second focal point in front of the crystallinelens of the pupil, through a polarizing plate, and reaches the retina.As a result, the user can observe an image.

CITATION LIST Patent Literature

Patent Literature 1: JP H05-134208A

DISCLOSURE OF INVENTION Technical Problem

Incidentally, different observers have different inter-eyeballdistances. Therefore, the position of an image display device isadjusted in the eyeball direction of the observer (the direction of aline connecting the centers of the two eyeballs of the observer). Forexample, when it is assumed that an original image shown in FIG. 14A isobserved by the right eye, then if the position adjustment is not mostsuitable, the image may be distorted as schematically shown in FIG. 14B.

Therefore, it is an object of the present disclosure to provide an imagedisplay device which has a configuration and structure which are lesslikely to cause a distortion in an observed image when the position ofthe image display device in the eyeball direction of an observer isadjusted, and a display apparatus employing such an image displaydevice.

Solution to Problem

To achieve the above described object, an image display device accordingto the present disclosure includes:

(A) an image formation device; and

(B) an optical system that brings an image from the image formationdevice to an eyeball of an observer.0 (degrees)≤ω₂<ω₁is satisfied where

an image-formation-device first strike point is defined as a point wherean extended line of an optical axis of the optical system intersectswith an image exit surface of the image formation device,

a first normal line is defined as a normal line to the image exitsurface of the image formation device passing through theimage-formation-device first strike point,

an image-formation-device second strike point is defined as a pointwhere an extended line of a pupil center line of the eyeball of theobserver intersects with the image exit surface of the image formationdevice,

a second normal line is defined as a normal line to the image exitsurface of the image formation device passing through theimage-formation-device second strike point, and

ω₁ represents an angle between the extended line of the optical axis ofthe optical system and the first normal line, and ω₂ represents an anglebetween the extended line of the pupil center line of the eyeball of theobserver and the second normal line.

To achieve the above object, a display apparatus of the presentdisclosure includes:

(i) a frame; and

(ii) an image display device attached to the frame.

The image display device includes the image display device of thepresent disclosure.

Advantageous Effects of Invention

In the image display device of the present disclosure, or the imagedisplay device included in the display apparatus of the presentdisclosure, the angle ω₁ between the extended line of the optical axisof the optical system and the first normal line, and the angle ω₂between the extended line of the pupil center line of the eyeball of theobserver and the second normal line, satisfy the predeterminedrelationship. Specifically, the extended line of the pupil center line(line-of-sight forward optical line) of the eyeball of the observer issubstantially orthogonal to the image exit surface of the imageformation device. Therefore, when the position of the image displaydevice in the eyeball direction (x-axis direction) of the observer isadjusted, an image observed by the observer only translates in adirection substantially orthogonal to the extended line of the pupilcenter line (line-of-sight forward optical line), and therefore, theobserved image is less likely to be distorted. Note that theadvantageous effects described herein are merely illustrative andnon-limiting, and additional advantageous effects may be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A and FIG. 1B are conceptual diagrams for describing a displayapparatus and image display device of Example 1.

FIG. 2 is a conceptual diagram of a display apparatus and image displaydevice of Example 1.

FIG. 3 is a conceptual diagram of a display apparatus and image displaydevice of Example 2.

FIG. 4A, FIG. 4B, and FIG. 4C are diagrams schematically showingrelative positions and resolutions of an image viewed by each of theright eye and the left eye in a display apparatus of Example 1, adisplay apparatus of Example 2, and a conventional display apparatus.

FIG. 5 is a perspective view of main portions of a display apparatus ofExample 1 as it is worn by an observer.

FIG. 6 is a perspective view of a portion of a display apparatus ofExample 1.

FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D are a bottom view, top view,right side view, and rear view, respectively, of a display apparatus ofExample 1.

FIG. 8 is a perspective view of main portions of a display apparatus ofExample 3 as it is worn by an observer.

FIG. 9 is a diagram conceptually showing a situation where a distancebetween an image formation device and an optical system is adjustedusing an image-formation-device-and-reflecting-mirror-distanceadjustment device.

FIG. 10A and FIG. 10B are schematic diagrams of animage-formation-device-and-reflecting-mirror-distance adjustment device.

FIG. 11 is a conceptual diagram of a reflecting mirror and the like fordescribing where a reflecting mirror is located.

FIG. 12A and FIG. 12B are conceptual diagrams of a reflecting mirror andthe like for describing where a reflecting mirror is located, followingFIG. 11.

FIG. 13A, FIG. 13B, FIG. 13C, and FIG. 13D are conceptual diagrams fordescribing what an image to be observed is like, in the presence orabsence of correction of a distortion of an image signal, in adistortion correction device.

FIG. 14A and FIG. 14B are diagrams schematically showing what image isobserved in a conventional virtual-image display apparatus.

MODE(S) FOR CARRYING OUT THE INVENTION

The present disclosure will now be described by way of example withreference to the drawings. The present disclosure is not limited toexamples below. Various numerical values and materials in the examplesare merely illustrative. Note that description will be provided in thefollowing order.

-   1. Overview of image display device and display apparatus of the    present disclosure-   2. Example 1 (An image display device and display apparatus of the    present disclosure. A display apparatus having a third configuration    of the present disclosure)-   3. Example 2 (A variation of Example 1)-   4. Example 3 (A variation of Example 1 and Example 2. A display    apparatus having a first configuration of the present disclosure)-   5. Example 4 (A variation of Example 1 to Example 3. A display    apparatus having a second configuration of the present disclosure)-   6. Others    <Overview of Image Display Device and Display Apparatus of the    Present Disclosure>

In an image display device of the present disclosure and an imagedisplay device in a display apparatus of the present disclosure (thesedevices are hereinafter collectively referred to as the “image displaydevice or the like of the present disclosure”),0 (degrees)≤ω₂<1 (degrees)is preferably satisfied, although this is non-limiting.

The image display device or the like of the present disclosure includingthe preferable form further includes a reflecting mirror configured toreflect an image from an image formation device. An optical system canbe located (inserted) between the eyeballs of an observer and thereflecting mirror, can include lens group which an image reflected bythe reflecting mirror enters, and can be configured so that the opticalaxis of the lens group corresponds to the optical axis of the opticalsystem. Alternatively, the optical system can also include an aperture.In these cases, the optical system can be configured to additionallyinclude an optical member having a freeform surface which is located(inserted) between the reflecting mirror and the lens group (or theoptical system). Here, a specific example of the optical member can be alens-shaped member or a prism-shaped member. The optical member canconfigured to have a thickness in the light transmission direction whichchanges from the inside (the nose of the observer) toward the outside ina horizontal direction (an xy-plane described below). Furthermore, thefreeform surface of the optical member can be configured to have anodd-order curved surface in the horizontal direction. By inserting theoptical member, variations in an optical distance (optical path length)between various points on the image exit surface of the image formationdevice and the eyeball of the observer, can be reduced.

Note that, in other words, the optical axis of the optical system refersto a single axial line on which a light beam which enters the opticalsystem and exits the optical system is located. Also, the pupil centerline (line-of-sight forward optical line) of each eyeball of theobserver is a straight line which is parallel to a perpendicularbisector of a straight line connecting the rotation centers of the leftand right eyeballs, passing through the rotation center of the eyeball,and is parallel to a y-axis described below. Alternatively, the pupilcenter line (pupillary axis) is defined as a straight line which isperpendicular to the surface of the cornea, passing through the entrancepupil center of the eyeball.

Furthermore, in the image display device or the like of the presentdisclosure having the various preferable forms and configurationsdescribed above, the reflecting mirror can be in a form having afreeform surface, or alternatively, the reflecting mirror can be in aform having a concave surface. By imparting these forms to thereflecting mirror, variations in the optical distance (optical pathlength) between various points on the image exit surface of the imageformation device and the eyeball of the observer, can also be reduced.

Furthermore, the image display device or the like of the presentdisclosure having the various preferable forms and configurationsdescribed above can have a form in which a point where the optical axisof the optical system intersects with the surface of the lens groupfacing the observer is located closer to the outside than is the pupilcenter line of the eyeball of the observer.

Furthermore, the image display device or the like of the presentdisclosure having the various preferable forms and configurationsdescribed above can have a form in which 0<ω₃ is satisfied, where ω₃represents an angle between an image of the optical axis of the opticalsystem which is projected onto a horizontal surface (an xy-planedescribed below) and an image of the pupil center line of the eyeball ofthe observer which is projected onto the horizontal surface (thexy-plane described below). Also, ω₁ and ω₃ preferably satisfies thefollowing relationship:0 (degrees)≤|ω₁-ω₃|≤1 (degrees)

The display apparatus of the present disclosure having the variouspreferable forms and configurations described above can have a form inwhich a left-eye image display device and a right-eye image displaydevice are attached to a frame. The left-eye image display device andthe right-eye image display device can each include the image displaydevice of the present disclosure having the various preferable forms andconfigurations described above. Note that such a display apparatus isreferred to as the “binocular display apparatus” for the sake ofconvenience. Here, the binocular display apparatus can have a form inwhich a normal line to the reflecting mirror included in the left-eyeimage display device intersects with a normal line to the reflectingmirror included in the right-eye image display device in a space on theopposite side of the reflecting mirrors from the observer. Note thatsuch a form is referred to as a “display apparatus having a firstconfiguration of the present disclosure” for the sake of convenience. Inthis case, a form can be provided in which the normal line to thereflecting mirror included in the left-eye image display deviceintersects with the normal line to the reflecting mirror included in theright-eye image display device below a virtual surface (the xy-planedescribed next) including both eyeballs of the observer and a point atinfinity. By employing such a form, the two image formation devices canbe easily located side by side with a high flexibility of design. In thebinocular display apparatus, the image formation device included in theleft-eye image display device and the image formation device included inthe right-eye image display device may be integrated together.

Also, in the above preferable embodiment of the display apparatus havingthe first configuration of the present disclosure, the reflecting mirroris located as shown in FIG. 11, FIG. 12A, and FIG. 12B, specifically asfollows.

An xy-plane is defined as a virtual surface including both eyeballs ofthe observer and a point at infinity. An x-axis is defined as a straightline connecting both eyeballs of the observer (specifically, the x-axisis defined as an axial line which is a straight line connecting botheyeballs of the observer, extending from the right eyeball toward theleft eyeball of the observer). A y-axis is defined as the pupil centerline of the right eye of the observer (specifically, the y-axis isdefined as an axial line which is orthogonal to the x-axis, extendingtoward the lens group). A “right-eye reflecting mirror optical axisstrike point” is defined as a point on the reflecting mirror where theoptical axis (main optical axis) of the lens group in the right-eyeimage display device strikes the reflecting mirror. It is assumed thatthe reflecting mirror in the right-eye image display device is locatedparallel (vertically) to an xz-plane (see FIG. 11). Furthermore, aζ-axis is defined as an axial line on the reflecting mirror which isparallel to the xy-plane, passing through the right-eye reflectingmirror optical axis strike point. A η-axis is defined as an axial lineon the reflecting mirror which is orthogonal to the ξ-axis, passingthrough the right-eye reflecting mirror optical axis strike point (seeFIG. 11).

In this case, a plane mirror in the right-eye image display device isrotated about the ζ-axis by an angle of θ₁ of 45 degrees±5 degrees withthe top of the plane mirror being rotated in a direction away from theobserver (see a dash-dot line in FIG. 12A indicating states beforerotation of the reflecting mirror and the axial line, and a solid lineand a dotted line in FIG. 12A indicating states after rotation of thereflecting mirror and the axial line), and is rotated about the η-axisby an angle θ₂ of 7 degrees to 21 degrees with the right end of theplane mirror being rotated in a direction away from the observer (see adash-dot line in FIG. 12B indicating states before rotation of thereflecting mirror and the axial line, and a solid line and a dotted linein FIG. 12B indicating states after rotation of the reflecting mirrorand the axial line).

The image formation device, optical system, and reflecting mirror of theleft-eye image display device can have a form in which they and theimage formation device, optical system, and reflecting mirror of theright-eye image display device are mirror-symmetrical about a virtualsurface which is parallel to a yz-plane, passing through the midpoint ofa line segment connecting both eyeballs of the observer. Furthermore,when a ξ-axis is defined as an axial line orthogonal to the ζ-axis andthe η-axis, an example of a relationship between an angle θ₃ between anaxial line (ξ-axis) obtained by projecting the ξ-axis onto the xy-planeand the y-axis, and the angle θ₁ and the angle θ₂, is shown in Table 1below. The angle θ₃ takes a positive value in the (−x, y) quadrant (seeFIG. 11 and FIG. 12A). The optical axis (main optical axis) of the lensgroup preferably intersects with the center of the eyeball of observer.Furthermore, in these preferable forms, a form is preferable in whichthe image formation device is located above the reflecting mirror. Notethat the ξ-axis coincides with the optical axis (main optical axis) ofthe lens group, and the angle θ₃ is equal to the angle ω₃.

TABLE 1 θ₁ (degrees) θ₂ (degrees) θ₃ (degrees) 45 5 9 45 10 15 45 15 2245 18 25 45 20 29

The image exit surface of the image formation device may be flat.Alternatively, the image formation device can have a form in which theimage exit surface of the image formation device is curved in anX-direction, in a Y-direction, or in both the X-direction and theY-direction, where the X-direction is defined as a direction of theimage formation device corresponding to a first direction of an image,and the Y-direction is defined as a direction of the image formationdevice corresponding to a second direction of the image different fromthe first direction. Note that an image of the X-direction projectedonto the xy-plane is parallel to the x-axis, and an image of theY-direction projected onto the xy-plane is parallel to the y-axis.

In the display apparatuses of the present disclosure having the variouspreferable forms and configurations described above (the displayapparatus having the first configuration of the present disclosure, adisplay apparatus having a second configuration of the presentdisclosure described below, and a display apparatus having a thirdconfiguration of the present disclosure described below):

the image formation device has a rectangular outer shape; and

wiring extends to the outside from an outer peripheral portion of theimage formation device extending in the Y-direction. Here, an example ofthe wiring can be a flexible printed wiring board (FPC). A connectionsection provided in the outer peripheral portion of the image formationdevice may be connected with the wiring using a well-known technique.

Also, the display apparatuses of the present disclosure having thevarious preferable forms and configurations described above (includingthe display apparatus having the first configuration of the presentdisclosure), each image display device can be configured to have animage-formation-device-and-reflecting-mirror-distance adjustment devicefor adjusting a distance between the image formation device and thereflecting mirror. Note that the display apparatus of the presentdisclosure having such a configuration is referred to as the “displayapparatus having the second configuration of the present disclosure” forthe sake of convenience. Here, by providing theimage-formation-device-and-reflecting-mirror-distance adjustment device,a difference in vision between each observer, depending on the observer,can be appropriately and easily dealt with, although the device has asimple configuration and structure. Also, the display apparatus havingthe second configuration of the present disclosure can be configured tofurther include a display control device for controlling a size of anentire image from the image formation device, depending on the distancebetween the image formation device and the reflecting mirror. For thedistance between the image formation device and the reflecting mirror,the image-formation-device-and-reflecting-mirror-distance adjustmentdevice may be provided with a distance detection device for detectingthe distance between the image formation device and the reflectingmirror. The distance detection device may be suitably adapted, dependingon the configuration and structure of theimage-formation-device-and-reflecting-mirror-distance adjustment device.A size of an entire image can be controlled using a well-known controltechnique, such as enlarging/reducing a size of an entire image, byperforming various signal processes (e.g., decimation or interpolation)on an image signal which is used to form an image in the image formationdevice.

Also, in the display apparatuses of the present disclosure having thevarious preferable forms and configurations described above (includingthe display apparatus having the first configuration of the presentdisclosure, and the display apparatus having the second configuration ofthe present disclosure), each image display device can be configured toinclude an eyeball-and-lens-group-distance adjustment device foradjusting a distance between the lens group and the eyeball of observer.Note that the display apparatus of the present disclosure having such aconfiguration is referred to as the “display apparatus having the thirdconfiguration of the present disclosure” for the sake of convenience.Here, by providing the eyeball-and-lens-group-distance adjustmentdevice, the distance between the eyeball of the observer and the lensgroup can be can be appropriately and easily adjusted and regulated,although the device has a simple configuration and structure.

Also, in the display apparatuses of the present disclosure having thevarious preferable forms and configurations described above (includingthe display apparatus having the first configuration of the presentdisclosure, the display apparatus having the second configuration of thepresent disclosure, and the display apparatus having the thirdconfiguration of the present disclosure), the image display device canbe configured to further include a rotation device for rotating theimage formation device about at least one of an X-axis, Y-axis, andZ-axis, where the X-axis is defined as an axis which is parallel to theX-direction, passing through a predetermined point (e.g., an imageformation device-optical axis strike point described below) of the imageformation device, and the Y-axis is defined as an axis which is parallelto the Y-direction, passing through a predetermined point (e.g., theimage formation device-optical axis strike point) of the image formationdevice. Specifically, such a rotation device can, for example, be arotation device for rotating the image formation device about theX-axis, a rotation device for rotating the image formation device aboutthe Y-axis, a rotation device for rotating the image formation deviceabout the Z-axis, a rotation device for rotating the image formationdevice about the X-axis and the Y-axis, a rotation device for rotatingthe image formation device about the X-axis and the Z-axis, a rotationdevice for rotating the image formation device about the Y-axis and theZ-axis, or a rotation device for rotating the image formation deviceabout the X-axis, the Y-axis, and the Z-axis. Furthermore, when such aconfiguration is possessed by the display apparatuses of the presentdisclosure having the various preferable forms and configurationsdescribed above (including the display apparatus having the firstconfiguration of the present disclosure, the display apparatus havingthe second configuration of the present disclosure, and the displayapparatus having the third configuration of the present disclosure), thedisplay apparatuses can be configured to further include a movementdevice for moving the image formation device in the X-direction withrespect to the reflecting mirror. When these preferable configurationsare possessed by the display apparatuses of the present disclosurehaving the various preferable forms and configurations described above(including the display apparatus having the first configuration of thepresent disclosure, the display apparatus having the secondconfiguration of the present disclosure, and the display apparatushaving the third configuration of the present disclosure), the displayapparatuses can be configured to further include aninter-image-display-device-distance adjustment device for adjusting adistance between the left-eye image display device and the right-eyeimage display device. By providing theinter-image-display-device-distance adjustment device, observers havingdifferent inter-eyeball distances can be easily dealt with.

Furthermore, the display apparatuses of the present disclosure havingthe various preferable forms and configurations described aboveincluding the display apparatus having the first configuration of thepresent disclosure, the display apparatus having the secondconfiguration of the present disclosure, and the display apparatushaving the third configuration of the present disclosure (these arehereinafter collectively referred to as the “display apparatuses and thelike of the present disclosure”), can have a form in which the frame ismounted on the observer's head. Note that the present disclosure is notlimited to such a form. For example, the frame may be attached to an armextending from a ceiling or wall, or may be attached to a freely-movablerobot arm. Also, a motion of the observer's head may be detected using asensor, and a motion of the frame may be caused to follow the motion ofthe observer's head.

In the case of the form in which the frame is mounted on the observer'shead, the frame can be of any type if the frame has a configuration andstructure which allow the frame to be attached to the observer's head,and in addition, allow the image display device to be attached to theframe. For example, the frame can be configured to include a frontsection which is to be located in front of the observer, and a sidesection extending from either end of the front section. The imagedisplay device is attached to the frame. Specifically, for example, theimage display device is attached to a holding member which is attachedto a lower portion of the front section, extending in a generallyhorizontal direction. Also, a forehead pad which is made contact withthe observer's forehead is desirably attached to an upper portion of thefront section, in order to improve the observer's feeling of attachmentof the image display device.

Furthermore, in the display apparatuses of the present disclosure havingthe various preferable forms and configurations described above and thelike, an overlap (binocular angle of view) between the horizontal fieldof view of the left-eye image display device and the horizontal field ofview of the right-eye image display device can, for example, be 45degrees to 100 degrees.

Furthermore, in the display apparatuses of the present disclosure havingthe various preferable forms and configurations described above and thelike, the image formation device can be of any type. The image formationdevice can, for example be: an image formation device including areflective spatial light modulation device and a light source; an imageformation device including a transmissive spatial light modulationdevice and a light source; or an image formation device including alight emitting device, such as a light emitting diode (LED),semiconductor laser device, organic electroluminescence (EL) device,inorganic EL device, or the like. The spatial light modulation devicecan, for example, be a light bulb, a transmissive or reflective liquidcrystal display device, such as liquid crystal on silicon (LCOS) or thelike, or a digital micromirror device (DMD). The light source can, forexample, be the above light emitting device. The reflective spatiallight modulation device can, for example, be configured to include aliquid crystal display device, and a polarizing beam splitter whichreflects a portion of light from the light source and guides the portionof light to the liquid crystal display device, and transmits a portionof light reflected by the liquid crystal display device and guides theportion of light to the optical system. The light emitting deviceincluded in the light source can, for example, be a red light emittingdevice, green light emitting device, blue light emitting device, orwhite light emitting device. Alternatively, red light, green light, andblue light emitted from a red light emitting device, green lightemitting device, and blue light emitting device may be mixed, and theirluminances may be homogenized, using light pipes, to obtain white light.Also, such a light emitting device can, for example, be a semiconductorlaser device, solid-state laser, or LED.

Alternatively, the image formation device can have a form in which itincludes a light source and a scanning means for scanning parallel raysemitted from the light source. Here, the light source can be a lightemitting device. Specifically, the light source can be a red lightemitting device, green light emitting device, blue light emittingdevice, or white light emitting device. Alternatively, red light, greenlight, and blue light emitted from a red light emitting device, greenlight emitting device, and blue light emitting device may be mixed, andtheir luminances may be homogenized, using light pipes, to obtain whitelight. Such a light emitting device can, for example, be a semiconductorlaser device, solid-state laser, or LED. When a color image isdisplayed, and the light source includes a red light emitting device, agreen light emitting device, and a blue light emitting device, a coloris preferably synthesized using, for example, a cross prism. Thescanning means can be a microelectromechanical system (MEMS) orgalvano-mirror which horizontally and vertically scans light emittedfrom the light source, and has, for example, a micromirror which can berotated in a two-dimensional direction.

In the display apparatuses and the like of the present disclosure, adisplay region of the image formation device has a length L_(x) of 83 mmto 130 mm in the X-direction. The number of pixels in the imageformation device can, for example, be 320×240, 432×240, 640×480,1024×768, 1920×1080, 3840×2160, or the like, and the aspect ratiothereof can, for example, be 4:3, 16:9, or alternatively, 21:9 or thelike. The horizontal angle of view (monocular angle of view) of theimage display device can, for example, be 100 degrees to 120 degrees.

Example 1

Example 1 relates to the display apparatus and image display device ofthe present disclosure, and further, to the display apparatus having thethird configuration of the present disclosure. FIG. 1A, FIG. 1B, andFIG. 2 show conceptual diagrams of general configurations of the displayapparatus and image display device of Example 1 (diagrams of the imagedisplay device as viewed from above). Also, FIG. 5 shows a perspectiveview of main portions of the display apparatus as it is worn by theobserver. Furthermore, FIG. 6 shows a perspective view of a portion ofthe display apparatus of Example 1. In FIG. 6, the reflecting mirror,the image formation device, and the like are not shown. Also, FIG. 7A,FIG. 7B, FIG. 7C, and FIG. 7D show a bottom view, top view, right sideview, and rear view of the display apparatus of Example 1, where aportion of the constituent elements of the image formation device andthe display apparatus are not shown for sake of simplicity.

The image display device 30 (30L, 30R) of Example 1 includes:

(A) an image formation device 40 (40L, 40R); and

(B) an optical system 50 for bringing an image from the image formationdevice 40 (40L, 40R) to an eyeball 11 (11L, 11R) of an observer 10, inwhich0 (degrees)≤ω₂<ω₁is satisfied where

an image-formation-device first strike point CP₁ is defined as a pointwhere an extended line of the optical axis of the optical system 50intersects with an image exit surface 40′ of the image formation device40 (40L, 40R),

a first normal line NL₁ is defined as a normal line to the image exitsurface 40′ of the image formation device 40 (40L, 40R) passing throughthe image-formation-device first strike point CP₁,

an image-formation-device second strike point CP₂ is defined as a pointwhere an extended line of the pupil center line of the eyeball of theobserver 10 intersects with the image exit surface 40′ of the imageformation device 40 (40L, 40R),

a second normal line NL₂ is defined as a normal line to the image exitsurface 40′ of the image formation device 40 (40L, 40R) passing throughthe image-formation-device second strike point CP₂, and

ω₁ represents an angle between the extended line of the optical axis ofthe optical system 50 and the first normal line NL₁, and ω₂ representsan angle between the extended line of the pupil center line of theeyeball of the observer 10 and second normal line NL₂.

The display apparatus of Example 1 includes:

(i) a frame 20; and

(ii) an image display device attached to the frame 20,

in which

the image display device includes the image display devices 30 (30L,30R) of Example 1. The frame 20 of the display apparatus of Example 1 isworn on the head of the observer 10. More particularly, the displayapparatus of Example 1 is a head mounted display (HMD) and a binoculardisplay apparatus. Note that constituent elements of the left-eye imagedisplay device are each indicated by a reference sign with a suffix “L,”and constituent elements of the right-eye image display device are eachindicated by a reference sign with a suffix “R.”

Here, ω₂ satisfies:0 (degrees)≤ω₂≤1 (degrees)

Specifically,ω₁=15 (degrees)ω₂=0 (degrees)θ₁=45 degreesθ₂=10 degrees

The image display device 30 further includes a reflecting mirror 51 forreflecting an image from the image formation device 40. The opticalsystem 50 includes lens group 52. The lens group 52 is located(inserted) between the eyeball 11 of the observer 10 and the reflectingmirror. An image reflected by the reflecting mirror 51 including a planemirror enters the lens group 52. The optical axis of the lens group 52corresponds to the optical axis of the optical system 50. Furthermore, apoint where the optical axis of the optical system 50 intersects with asurface of the lens group 52 facing the observer 10, is located closerto the outside than is the pupil center line of the eyeball of theobserver 10. When an angle between an image of the optical axis of theoptical system 50 which is projected onto the horizontal surface(xy-plane) and an image of the pupil center line of the eyeball of theobserver 10 which is projected onto the horizontal surface (xy-plane) isrepresented by ω₃, 0<ω₃ is satisfied. A specific example was:ω₃=θ₃=15 (degrees)

Note that ω₁ and ω₃ satisfies the following relationship:0 (degrees)≤|ω₁-ω₃|≤1 (degrees)

Incidentally, when the size of a pixel in the image formation device issubstantially the same, it is effective to increase the size of theimage formation device if a larger screen is desired. When, in thebinocular display apparatus, the extended line (line-of-sight forwardoptical line) of the pupil center line of the eyeball 11 of the observer10 is located orthogonal to the image exit surface 40′ of the imageformation device 40L, 40R, the increase in the size of the imageformation device is accompanied by overlapping of the image formationdevice 40L and the image formation device 40R, which makes it difficultto arrange the image formation devices 40L and 40R. This situation isshown in FIG. 1A which is a conceptual diagram of the image displaydevice and the like as viewed from above. Here, it is contemplated thatthe lens groups 52L and 52R and the image formation devices 40L and 40Rare inclined. This situation is shown in FIG. 1B which is a conceptualdiagram of the image display device and the like as viewed from above.Such an arrangement can provide a field of view which is similar to thatof a human eye, and enlarge the entire field of view. However, in suchan arrangement, the pupil center line (line-of-sight forward opticalline) of the eyeball of the observer is not orthogonal to the image exitsurface 40′ of the image formation device 40 (40L, 40R), and therefore,when a position of the image display device in the eyeball direction(x-axis direction) of the observer 10 is adjusted, an observed image isdistorted (see FIG. 14B). Note that, in FIG. 1A, FIG. 1B, and FIG. 2,and FIG. 3 described below, the reflecting mirror is not shown. Also,although the image formation device is shown in a vertical position, theimage formation device is actually in substantially a horizontalposition.

Meanwhile, in the display apparatus and image display device of Example1, as can be seen from FIG. 2 which is a conceptual diagram of the imagedisplay device and the like as viewed from above, the angle ω₁ betweenthe extended line of the optical axis of the optical system 50 and thefirst normal line, and the angle ω₂ between the extended line of thepupil center line of the eyeball of the observer 10 and the secondnormal line, satisfy the predetermined relationship. Specifically, theextended line (line-of-sight forward optical line) of the pupil centerline of the eyeball 11 of the observer 10 is substantially orthogonal tothe image exit surface 40′ of the image formation device 40. Therefore,when the position of the image display device in the eyeball direction(x-axis direction) of the observer 10 is adjusted, an image observed bythe observer 10 only translates in a direction substantially orthogonalto the extended line of the pupil center line (line-of-sight forwardoptical line), and therefore, the observed image is less likely to bedistorted. In addition, the resolution can be improved in a mostfrequent position of the eyeball (in front of the eye along the line ofsight), and therefore, an object to be observed can be seen in a morerealistic way, and images captured by both eyes can be more easilyfused. Furthermore, image distortion characteristics are flat in frontof the eye along the line of sight, and therefore, when the eyeball isturned, a difference in image distortion characteristics (may also behereinafter referred to as “image distortion characteristicsdifference”) is less likely to occur between the left-eye image displaydevice and the right-eye image display device. Also, a distorted imageas shown in FIG. 14B can be prevented, and therefore, it is notnecessary to correct an input image signal in order to correct adistorted image as shown in FIG. 14B.

FIG. 4A, FIG. 4B, and FIG. 4C schematically show positions in the x-axisdirection and resolutions of an image viewed by each of the right eyeand the left eye in the display apparatus of Example 1, a displayapparatus of Example 2, and a conventional display apparatus. Note that,in FIG. 4A, FIG. 4B, and FIG. 4C, “L” indicates a position on the x-axiswhere the highest resolution can be obtained in an image viewed by theleft eye, and “R” indicates a position on the x-axis where the highestresolution can be obtained in an image viewed by the right eye. Here,the conventional apparatus is a display apparatus (see FIG. 1B) whichsatisfies:0 (degrees)=ω₁<ω₂=15 (degrees)

The conventional apparatus is an example in a case where the positionadjustment of the image display device in the eyeball direction (x-axisdirection) of the observer (specifically, the adjustment of a relativeposition between the two image display devices in the eyeball directionof the observer on the basis of the inter-eyeball distance of theobserver) is not most suitable.

In the conventional display apparatus, an image viewed by the right eyeis separated from an image viewed by the left eye in the x-axisdirection, and as a result of fusion of the images, the images arerecognized as double images (see FIG. 4C). Meanwhile, in the displayapparatus of Example 1, an image viewed by the right eye coincides withan image viewed by the left eye in the x-axis direction, and as a resultof fusion of the images, the images are recognized as a single image(see FIG. 4A). Note that, in the display apparatus of Example 2described below, a range having a high resolution in the x-axisdirection is wider than in the display apparatus of Example 1. In otherwords, in the display apparatus of Example 2, the image distortioncharacteristics are flatter in front of the eye along the line of sight,and therefore, a difference in image distortion characteristics is lesslikely to occur when the eyeball is turned.

Specifically, in the display apparatus of Example 1, the image formationdevice 40 includes a liquid crystal display device having a well-knownconfiguration and structure. The liquid crystal display device includesa first substrate, a second substrate, and a large number of lightemitting units interposed between the first substrate and the secondsubstrate. The number of pixels of the image formation device 40 was1920×1080. The horizontal angle of view (monocular angle of view) ofeach image display device 30 (30L, 30R) was 100 degrees. The overlap(binocular angle of view) between the horizontal field of view of theleft-eye image display device 30L and the horizontal field of view ofthe right-eye image display device 30R was 70 degrees. The overallhorizontal angle of view was 130 degrees. The length L_(x) in theX-direction of the display region of each image formation device 40 was100 mm. Also, the vertical angle of view was 60 degrees.

Also, wiring, specifically a flexible printed wiring board (FPC),extends to the outside from an outer peripheral portion of the imageformation device 40 extending in the Y-direction. A connection sectionprovided in the outer peripheral portion of the image formation devicemay be connected with the wiring using a well-known technique.

The frame 20, which is worn on the head of the observer 10, is made ofplastic, and includes a front section 21 provided in front of theobserver 10, and a side section 22 extending from either end of thefront section. A hole section 22A is provided at a rear end portion ofeach side section 22. A belt is passed through the hole sections 22A,and is fasten at a rear portion of the observer's head, whereby theframe 20 can be worn on the head of the observer 10. An arm 23A extendsupward from an upper portion of the front section 21. A forehead pad 23Bwhich is made contact with the forehead of the observer 10 is attachedto a tip portion of the arm 23A. Furthermore, the front section 21 isprovided with a nose pad section 24. Also, a rear portion of the holdingmember 25 is attached to a lower end portion of the front section 21. Abase 26 is attached to a front portion of the holding member 25.Furthermore, an eyeball-and-lens-group-distance adjustment device 80described below is attached to a tip portion of the base 26. A seat 71included in the eyeball-and-lens group-distance adjustment device 80 isprovided on the base 26 so that the seat 71 can freely slide forward andbackward. The optical system 50L included in the left-eye image displaydevice 30L is accommodated in a housing 53L. The optical system 50Rincluded in the right-eye image display device 30R is accommodated in ahousing 53R. The left-eye image display device 30L is attached to thehousing 53L. The left-eye image display device 30R is attached to thehousing 53R. The housing 53L and the housing 53R are attached to theseat 71. As described next, a pair of the optical system 50L and theleft-eye image display device 30L and a pair of the optical system 50Rand the right-eye image display device 30R are arranged so that eachpair can independently freely slide leftward and rightward on the seat71. Note that the term “forward and backward” means directions in whichthe lens group moves toward and away from the eyeball. The term“leftward and rightward” means directions in which the left-eye imagedisplay device and the right-eye image display device move toward oraway from each other.

As described above, the optical system 50 includes the lens group 52which an image reflected by the reflecting mirror 51 enters. Thereflecting mirror 51R and the lens group 52R included in the right-eyeimage display device are attached to the seat 71 with the housing 53Rbeing interposed therebetween, and can slide leftward and rightward onthe base 26. Similarly, the reflecting mirror 51L and the lens group 52Lincluded in the left-eye image display device are attached to the seat71 with the housing 53L being interposed therebetween, and can slideleftward and rightward on the base 26. The lens groups 52 (52R, 52L) arelocated between the eyeball 11 of the observer 10 and the reflectingmirror 51 (51R, 51L). The image formation device 40 is located above thereflecting mirror 51.

The lens group 52 includes a group of three lenses. The first lens (lensclosest to the observer) is a spherical lens having positive power, thesecond lens is a meniscus lens having negative power, and the third lens(closest to the reflecting mirror) is a freeform surface lens havingpositive power. Also, a material for the second lens has a higherrefractive index than those of materials for the first lens and thethird lens. The lens group 52 had a length of 50 mm in the horizontaldirection, and a length of 30 mm in the vertical direction. Here, adistance between the first lens and the eyeball (pupil diameter: 4 mm)of the observer 10 was 12 mm, the effective focal point distance was66.1 mm, the rear focal point distance was 7.13 mm, and the front focalpoint distance was 26.5 mm. Such a lens configuration allows a singleeye to have a horizontal angle of view of 100 degrees and a verticalangle of view of 60 degrees.

The display apparatus of Example 1 further includes aninter-image-display-device-distance adjustment device 70 for adjusting adistance between the left-eye image display device 30L and the right-eyeimage display device 30R, although this is not essential. Specifically,the inter-image-display-device-distance adjustment device 70 includesthe seat 71, a feed screw mechanism 73 attached to a side surface 72located outside the seat 71, a tapped hole 75A for fixing the housing 53to the seat 71 from bottom by a holding force which allows the housing53 to slide, guide grooves 74B and 76B provided in the housing 53, aguide groove 75B provided in the seat 71, and pins 74A and 76A providedon the seat 71 and engaging with the guide grooves 74B and 76B. Notethat the guide grooves 75B, 75B, and 76B extend in a lateral direction.When the feed screw mechanism 73 is rotated, the housing 53 (the housing53L or the housing 53R) moves leftward or rightward with respect to thebase 26. The leftward and rightward movements of the housing 53 arereliably performed by the engagement of the pin 74A, the tapped hole75A, and the pin 76A with the guide grooves 74B, 75B, and 76B. Themovement distance of the housing 53L, 53R in the horizontal directionwas ±5 mm. Thus, by providing the inter-image-display-device-distanceadjustment device 70, it is easy to deal with observers having differentinter-eyeball distances. Instead of the feed screw mechanism 73, acombination of a latch mechanism and a nob, or a rack-and-pinionmechanism, can be used. The housing 53R, 53L extends upward further thanit is shown in FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D. To this portionof the housing 53R, 53L extending upward, a support member forsupporting the image formation device 40 and the like are attached, butare not shown.

Also, the display apparatus of Example 1 further includes aneyeball-and-lens-group-distance adjustment device 80 between the eyeballof the observer 10 and the lens group 52, although this is notessential. Specifically, the eyeball-and-lens-group-distance adjustmentdevice 80 adjusts a distance between the lens group 52 and the eyeballof the observer 10. More specifically, theeyeball-and-lens-group-distance adjustment device 80 includes a sidewall 82 attached to a tip portion of the holding member 25, a feed screwmechanism 83 attached to the side wall 82, a key 27A provided on theseat 71, extending downward from the seat 71, a guide groove 27Bprovided in the base 26, engaging the key 27A, and a fastening section27C for holding the seat 71 at a level which allows the seat 71 to slidewith respect to the base 26. When the feed screw mechanism 83 isrotated, the seat 71 moves forward or backward with respect to the base26. The leftward and rightward movements of the seat 71 are reliablyperformed by the engagement of the key 27A with the guide groove 27B.The forward and backward movement distances of the seat 71 were ±4 mm.Thus, by providing the eyeball-and-lens-group-distance adjustment device80, it is easy to deal with observers having different distances betweenthe eyeball and the lens group. Therefore, a display apparatus can beprovided in which the distance between the eyeball of the observer andthe lens group can be appropriately and easily adjusted and regulated,although it has a simple configuration and structure. Instead of thefeed screw mechanism 83, a combination of a latch mechanism and a nob,or a rack-and-pinion mechanism, can be used.

Example 2

Example 2 is a variation of Example 1. As shown in FIG. 3 which is aconceptual diagram of an image display device and the like as viewedfrom above, a display apparatus or image display device of Example 2 hasan optical member 54 having a freeform surface which is located(inserted) between the reflecting mirror 51 and the lens group 52 (orthe optical system 50). Here, specifically, as the optical member 54, aprism-shaped member was used. A thickness in the light transmissiondirection of the optical member 54 changes in the horizontal direction(xy-plane) from the inside (closer to the nose of the observer 10)toward the outside. Specifically, the thickness becomes smaller from theinside toward the outside. The freeform surface (surface along thexz-plane) of the optical member 54 has an odd-order surface in thehorizontal direction (xy-plane). Specifically, in a polynominal of x,the coefficient of the first-order term of x is “0,” and thecoefficients of the second-order and higher terms of x are not zero.Also, in a polynominal of z of a surface, the coefficients of theodd-order terms of z are “0,” and the coefficients of the even-orderterms of z are not zero. By thus inserting the optical member 54,variations in optical distance (optical path lengths) between variouspoints on the image exit surface 40′ of the image formation device 40and the eyeball 11 of the observer 10 can be reduced, so that thedistortion of an image can be further reduced, and the upper and lowerfields of view can be enlarged. Also, images captured by the two eyescan be more easily fused, and the image distortion characteristics areflat in front of the eye along the line of sight, and therefore, whenthe eyeball is turned, a difference in image distortion characteristicsis even less likely to occur. Note that it is preferable to perform akind of weighting using a turned state of the eyeball as a parameter,and design the freeform surface.

Alternatively, the reflecting mirror 51 can have a form in which it hasa freeform surface. Alternatively, the reflecting mirror 51 can have aform in which it has a concave surface. When the reflecting mirror havethese forms, variations in optical distance (optical path lengths)between various points on the image exit surface 40′ of the imageformation device 40 and the eyeball 11 of the observer 10 can bereduced. Note that when the reflecting mirror 51 has a form in which ithas a concave surface, rays located at a peripheral portion of the fieldof view can be caused to reliably reach the eyeball of the observer, andit is no longer necessary to unnecessarily increase the size of theimage display device in order to enlarge the field of view. Thereflecting mirror 51 having a freeform surface and the optical member 54having a freeform surface may be provided.

Example 3

Example 3 is a variation of Example 1 and Example 2, and relates to thedisplay apparatus having the first configuration of the presentdisclosure. FIG. 8 shows a perspective view of main portions of adisplay apparatus of Example 3 as it is worn by the observer.

In the display apparatus or image display device of Example 3, a normalline NL_(R) to the reflecting mirror 51 included in the left-eye imagedisplay device 30R intersects with a normal line NL_(L) to thereflecting mirror 51 included in right-eye image display device 30R in aspace on the opposite side of the reflecting mirrors 51 from theobserver 10. Furthermore, the normal line NL_(L) to the reflectingmirror 51 in the left-eye image display device 30L intersects with thenormal line NL_(R) to the reflecting mirror 51 in the right-eye imagedisplay device 30 below the virtual surface (xy-plane) including botheyeballs 11 of the observer 10 and a point at infinity. The imageformation device 40 is located above the reflecting mirror 51. Thereflecting mirror 51 is located as shown in FIG. 11, FIG. 12A, and FIG.12B. Specifically, in Example 1, the length L_(x) of the display regionof the image formation device 40 was 100 mm, andω₁=15 degreesω₂=0 degreesθ₁=45 degreesθ₂=10 degreesθ₃=ω₃=15 degrees

Note that, in the example, the reflecting mirror optical axis strikepoint is included in the xy-plane. Under such setting conditions, thereis a gap of about 15 mm between the image formation device 40 includedin the left-eye image display device 30L and the image formation device40 included in the right-eye image display device 30R, and the two imageformation devices can be arranged side by side. Also, the length L_(x)of the display region of the image formation device 40 may be 126 mm,andω₁=25 degreesω₂=0 degreesθ₁=45 degreesθ₂=18 degreesθ₃=ω₃=25 degrees

In this case, there is a gap of about 15 mm between the image formationdevice 40 included in the left-eye image display device 30L and theimage formation device 40 included in the right-eye image display device30R, and the two image formation devices can be arranged side by side.By employing such a form, the two image formation devices 40 can beeasily arranged side by side with a high flexibility of design.

In a case where (see FIG. 1A):ω₁=0 degreesω₂=0 degreesθ₁=45 degreesθ₂=0 degreesθ₃=ω₃=0 degreesand the length L_(x) in the X-direction of the display region of theimage formation device 40 is 100 mm, and the distance between the pupilcenter line of the left eye of the observer and the pupil center line ofthe right eye of the observer is 65 mm, the image formation device 40included in the left-eye image display device 30L and the imageformation device 40 included in the right-eye image display device 30Roverlap by about 35 mm[=50 30 50−65 (mm)]. The image formation devicescannot be arranged side by side.

Example 4

Example 4 is a variation of Example 1 to Example 3, and relates to thedisplay apparatus having the second configuration of the presentdisclosure. In a display apparatus of Example 4, each image displaydevice 30 further includes animage-formation-device-and-reflecting-mirror-distance adjustment device90 for adjusting a distance between the image formation device 40 andthe reflecting mirror 51.

As described above, a support member or the like for supporting theimage formation device 40 is attached to the portion of the housing 53R,53L extending upward. As shown in FIG. 10A, for example, theimage-formation-device-and-reflecting-mirror-distance adjustment device90 includes an adjustment device base member 91, a shaft 92 attached toa support member 60, a feed screw mechanism 95 attached to theadjustment device base member 91, and a shaft 94 extending from the feedscrew mechanism 95 and attached to the support member 60. The supportmember 60 allows the shaft 92 to freely slide by means of a bushing 93,and can thereby freely change a distance between the support member 60and the adjustment device base member 91. The adjustment device basemember 91 is attached to the portion of the housing 53R, 53L extendingupward. By rotating the feed screw mechanism 95, the shaft 94 is movedin the vertical direction in the figure, so that the distance betweenthe adjustment device base member 91 and the support member 60 can bechanged. The movement of the support member 60 in the vertical directionin the figure is limited by the shaft 92 with the bushing 93.

Alternatively, as shown in FIG. 10B, for example, theimage-formation-device-and-reflecting-mirror-distance adjustment device90 includes a latch mechanism 96, and a pin 97 engaging with the latchmechanism. When the pin 97 is moved leftward in the figure (see an arrowin FIG. 10B), the pin 97 is disengaged from the latch mechanism 96. Whenthe pin 97 is moved rightward in the figure after the support member 60is moved in the vertical direction in the figure, the pin 97 engageswith the latch mechanism 96.

Thus, by using the image-formation-device-and-reflecting-mirror-distanceadjustment device 90 shown in FIG. 10A or FIG. 10B, the distance betweenthe image formation device 40 and the reflecting mirror 51 can beadjusted and regulated according to the observer's vision. Note that theimage-formation-device-and-reflecting-mirror-distance adjustment device90 shown in FIG. 10A or FIG. 10B is merely illustrative, and may be ofany type that can adjust the distance between the image formation deviceand the optical system. For example, instead of the bushing 93, a linearguide rail can be used, or a constraint mechanism between two planesarranged at right angles can be used. Also, instead of the feed screwmechanism 95 or the latch mechanism 96, a rack-and-pinion mechanism maybe employed.

For the distance between the image formation device 40 and thereflecting mirror 51, theimage-formation-device-and-reflecting-mirror-distance adjustment device90 may be provided with a distance detection device for detecting thedistance between the image formation device 40 and the reflecting mirror51. The distance detection device may be appropriately adapted,depending on the configuration and structure of theimage-formation-device-and-reflecting-mirror-distance adjustment device90. Specifically, for example, the distance detection device may be adevice for detecting a position (angle) of the feed screw mechanism 95,or a device for detecting a position of the pin 97 in the latchmechanism 96.

The display apparatus of Example 4 further includes a display controldevice (not shown) for controlling a size of an entire image from theimage formation device 40, depending on the distance between the imageformation device 40 and the reflecting mirror 51. Specifically, a sizeof an entire image from the image formation device 40 is decreased witha decrease in the distance between the image formation device 40 and thereflecting mirror 51. Note that a size of an entire image can becontrolled using a well-known control technique, such asenlarging/reducing a size of an entire image, by performing varioussignal processes on an image signal which is used to form an image inthe image formation device 40. The distance between the image formationdevice 40 and the reflecting mirror 51 may be detected using the abovedistance detection device.

FIG. 9 conceptually shows a relationship between the amount of amovement of the image formation device 40 with respect to the reflectingmirror 51 and a size of an entire image, i.e., a situation where thedistance between the image formation device and the optical system isadjusted using the image-formation-device-and-reflecting-mirror-distanceadjustment device. Compared to a case where the observer has a normalvision (diopter value: 0), when the observer is near-sighted, thedistance between the image formation device and the optical system isreduced. In this case, as shown in FIG. 9, a size of an entire imagefrom the image formation device 40 may be reduced. A relationshipbetween the diopter value, the amount of a movement of the imageformation device, and a size of an entire image (displayed image size)is shown in Table 2 below.

TABLE 2 Diopter value Movement amount Displayed image size −3 −9.4 mm 95.5 mm −2 −6.3 mm  9.8 mm −1 −3.1 mm 100.3 mm 0 0 103.4 mm 1 +3.1 mm106.7 mm 2 +6.3 mm 110.0 mm 3 +9.4 mm 113.8 mm

When the image formation device 40 (more specifically, the supportmember 60) is attached to the portion of the housing 53R, 53L extendingupward, it may be necessary to finely adjust the attachment of thesupport member 60. Note that it is typically necessary to do such a fineadjustment during assembly of the display apparatus. In such a case, theimage display device 30 may be provided with a rotation device forrotating the image formation device 40 about at least one of an X-axis,a Y-axis, and a Z-axis, where the X-axis is defined as an axis which isparallel to the X-direction, passing through a predetermined point(image formation device-optical axis strike point) of the imageformation device 40, and the Y-axis is defined as an axis which isparallel to the Y-direction, passing through a predetermined point(image formation device-optical axis strike point) of the imageformation device 40. An example of the rotation device can be acombination of a press screw and a pull screw which are attached to thehousing 53R, 53L. By finely adjusting the press screw and the pullscrew, the attachment of the support member 60 to the portion of thehousing 53R, 53L extending upward can be finely adjusted. For example,the image formation device 40 may be rotated about the X-axis by 40milliradians. The image formation device 40 may be rotated about theY-axis by 40 milliradians. The image formation device 40 may be rotatedabout the Z-axis by 40 milliradians. Also, if a guide groove is providedin the portion of the housing 53R, 53L extending upward, and a feedscrew mechanism is provided on the support member 60, i.e., a movementdevice including a guide groove and a feed screw mechanism is provided,the image formation device 40 can be moved in the X-direction withrespect to the reflecting mirror 51.

The display apparatus of Example 4 includes theimage-formation-device-and-reflecting-mirror-distance adjustment device.Therefore, a display apparatus can be provided which can appropriatelyand easily deal with a difference in vision between each observer,depending on the observer, although it has a simple configuration andstructure.

In the foregoing, the present disclosure has been described on the basisof preferable examples. The present disclosure is not limited to theseexamples. The configurations and structures of the display apparatus,image display device, and image formation device described in theexamples are merely illustrative, and changes and modifications can bemade thereto as appropriate. The image formation device and the supportmember for supporting the image formation device which have beendescribed in the examples can be combined to configure a projector.Also, instead of the reflecting mirror, a beam splitter (also called apartially reflective mirror, a partially transmissive mirror, asemi-transparent mirror, or a half-silvered mirror).

The display apparatus can have a form in which it includes a distortioncorrection device, and the distortion correction device corrects aninput image signal so that a distortion of an image to be observed iscorrected. FIG. 13A, FIG. 13B, FIG. 13C, and FIG. 13D show conceptualdiagrams for describing what an image to be observed is like in thedisplay apparatus, in the presence or absence of correction of adistortion of an image signal (correction of a display position). When adistortion of an image is not corrected, an image displayed on the imageformation device (see FIG. 13C) is finally observed in a form shown inby FIG. 13D by the observer 10. Specifically, a barrel-type distortionoccurs in an image observed by the observer 10. Meanwhile, when adistortion of an image is corrected, an image displayed on the imageformation device (see FIG. 13A) is finally observed in a form shown inFIG. 13B by the observer 10. Specifically, although a barrel-typedistortion occurs in an image observed by the observer 10, a bobbin-typedistortion has been originally imparted to the image displayed on theimage formation device (see FIG. 13A), and therefore, the observer 10can finally observe an image free from a distortion (see FIG. 13B). Thedistortion correction device is provided with a distortion correctioncoefficient table. The distortion correction coefficient table containsa list of relationships between a position (X_(Out), Y_(Out)) of anoutput image signal on the image formation device and a positioncorrection amount (ΔX_(Out), ΔY_(Out)) for the position (X_(Out),Y_(Out)). A correspondence relationship between a position on the imageformation device and an output image signal is acquired by thedistortion correction device. Next, the distortion correction devicelooks up a position correction amount (ΔX_(Out), ΔY_(Out)) correspondingto the acquired position (X_(Out), Y_(Out)) on the image formationdevice in the distortion correction coefficient table using the acquiredposition (X_(Out), Y_(Out)). Thereafter, a value of an image signalcorresponding to the corrected position (X_(Out)+ΔX_(Out),Y_(Out)+ΔY_(Out)) is calculated from the input image signal byextraction, interpolation, or the like, and the resulting value isdisplayed as a value at the position (X_(Out), Y_(Out)) on the imageformation device. The position correction amount (ΔX_(Out), ΔY_(Out))may be previously obtained by various simulations, experiments, or thelike. Thereafter, the distortion correction device corrects an inputimage signal, and thereby corrects a distortion of an image to beobserved. The distortion correction device corrects an input imagesignal to impart a barrel-type distortion or a bobbin-type distortion tothe input image signal to be corrected. In other words, the imageformation device 40 displays an image having a barrel-type distortion ora bobbin-type distortion. Specifically, the distortion correction devicecorrects at least image signals corresponding to both ends of the imageformation device 40 and portions located in the vicinity thereof, of aninput image signal, and thereby corrects at least distortions of animage at both ends of the image formation device 40 and portions locatedin the vicinity thereof. More specifically, image signals correspondingto both ends of the image formation device 40 and portions located inthe vicinity thereof are corrected. Here, the distortion correctiondevice itself can have a well-known circuit configuration, and isincluded in a control device (not shown) for controlling an operation ofthe display apparatus.

Additionally, the present technology may also be configured as below.[A01] <<Image Display Device>>

An image display device including:

(A) an image formation device; and

(B) an optical system that brings an image from the image formationdevice to an eyeball of an observer,

wherein0 (degrees)≤ω₂<ω₁is satisfied where

an image-formation-device first strike point is defined as a point wherean extended line of an optical axis of the optical system intersectswith an image exit surface of the image formation device,

a first normal line is defined as a normal line to the image exitsurface of the image formation device passing through theimage-formation-device first strike point,

an image-formation-device second strike point is defined as a pointwhere an extended line of a pupil center line of the eyeball of theobserver intersects with the image exit surface of the image formationdevice,

a second normal line is defined as a normal line to the image exitsurface of the image formation device passing through theimage-formation-device second strike point, and

ω₁ represents an angle between the extended line of the optical axis ofthe optical system and the first normal line, and ω₂ represents an anglebetween the extended line of the pupil center line of the eyeball of theobserver and the second normal line.

The image display device according to [A01],

wherein0 (degrees)≤ω₂≤1 (degrees)is satisfied.[A03]

The image display device according to [A01] or [A02], further including:

a reflecting mirror configured to reflect an image from the imageformation device, wherein

the optical system is located between the eyeball of the observer andthe reflecting mirror, and includes lens group which the image reflectedby the reflecting mirror enters, and

an optical axis of the lens group corresponds to the optical axis of theoptical system.

[A04]

The image display device according to [A03], further including:

an optical member that is located between the reflecting mirror and thelens group and that has a freeform surface.

[A05]

The image display device according to [A04],

wherein the optical member has a thickness that is along a lighttransmission direction and that changes in a horizontal direction froman inside toward an outside.

[A06]

The image display device according to [A05],

wherein the freeform surface of the optical member has an odd-ordercurved surface in a horizontal direction.

The image display device according to any one of [A03] to [A06],

wherein the reflecting mirror has a freeform surface.

The image display device according to any one of [A03] to [A06],

wherein the reflecting mirror has a concave surface.

[A09]

The image display device according to any one of [A03] to [A08],

wherein a point where the optical axis of the optical system intersectswith a surface of the lens group facing the observer is located closerto an outside than the pupil center line of the eyeball of the observer.

[A10]

The image display device according to any one of [A01] to [A09],

wherein0<ω₃is satisfied where

ω₃ represents an angle between an image projected onto a horizontalsurface of the optical axis of the optical system and an image projectedonto a horizontal surface of the pupil center line of the eyeball of theobserver.

[B01] <<Display Apparatus>>

A display apparatus including:

(i) a frame; and

(ii) an image display device that is attached to the frame,

wherein

the image display device includes

-   -   (A) an image formation device; and    -   (B) an optical system that brings an image from the image        formation device to an eyeball of an observer, and        0 (degrees)≤ω₂<ω₁        is satisfied where

an image-formation-device first strike point is defined as a point wherean extended line of an optical axis of the optical system intersectswith an image exit surface of the image formation device,

a first normal line is defined as a normal line to the image exitsurface of the image formation device passing through theimage-formation-device first strike point,

an image-formation-device second strike point is defined as a pointwhere an extended line of a pupil center line of the eyeball of theobserver intersects with the image exit surface of the image formationdevice,

a second normal line is defined as a normal line to the image exitsurface of the image formation device passing through theimage-formation-device second strike point, and

ω₁ represents an angle between the extended line of the optical axis ofthe optical system and the first normal line, and ω₂ represents an anglebetween the extended line of the pupil center line of the eyeball of theobserver and the second normal line.

[B02]

The display apparatus according to [B01],

wherein0 (degrees)≤ω₂≤1 (degrees)is satisfied.[B03]

The display apparatus according to [B01] or [B02], wherein the imagedisplay device further includes a reflecting mirror configured toreflect an image from the image formation device,

the optical system is located between the eyeball of the observer andthe reflecting mirror, and includes lens group which the image reflectedby the reflecting mirror enters, and

an optical axis of the lens group corresponds to the optical axis of theoptical system.

[B04]

The display apparatus according to [B03], wherein the image displaydevice further includes an optical member that is located between thereflecting mirror and the lens group and that has a freeform surface.

[B05]

The display apparatus according to [B04],

wherein the optical member has a thickness that is along a lighttransmission direction and that changes in a horizontal direction froman inside toward an outside.

[B06]

The display apparatus according to [B05],

wherein the freeform surface of the optical member has an odd-ordercurved surface in a horizontal direction.

[B07]

The display apparatus according to any one of [B03] to [B06],

wherein the reflecting mirror has a freeform surface.

[B08]

The display apparatus according to any one of [B03] to [B06],

wherein the reflecting mirror has a concave surface.

[B09]

The display apparatus according to any one of [B03] to [B08],

wherein a point where the optical axis of the optical system intersectswith a surface of the lens group facing the observer is located closerto an outside than the pupil center line of the eyeball of the observer.

[B10]

The image display device according to any one of [B01] to [B09],

wherein0<ω₃is satisfied where

ω₃ represents an angle between an image projected onto a horizontalsurface of the optical axis of the optical system and an image projectedonto a horizontal surface of the pupil center line of the eyeball of theobserver.

[C01]

<<Display Apparatus>>

The display device according to any one of [B01] to [B10], including:

a left-eye image display device and a right-eye image display deviceattached to the frame,

wherein

a normal line to a reflecting mirror included in an optical system ofthe left-eye image display device intersects with a normal line to areflecting mirror included in an optical system of the right-eye imagedisplay device, in a space on the opposite side of the reflectingmirrors from the observer.

[C02]

The display device according to [C01], wherein

the normal line to the reflecting mirror included in the optical systemof the left-eye image display device intersects with the normal line tothe reflecting mirror included in the optical system of the right-eyeimage display device, below a virtual surface including both eyeballs ofthe observer and a point at infinity.

[C03]

The display device according to [C01], wherein

an xy-plane is defined as a virtual surface including both eyeballs ofthe observer and a point at infinity, an x-axis is defined as a straightline connecting both eyeballs of the observer, a y-axis is defined as apupil center line of the right eye of the observer, a right-eyereflecting mirror optical axis strike point is defined as a point on thereflecting mirror where an optical axis of lens group in the right-eyeimage display device strikes the reflecting mirror, it is assumed thatthe reflecting mirror included in the right-eye image display device islocated parallel to an xz-plane, furthermore, a ζ-axis is defined as anaxial line on the reflecting mirror which is parallel to the xy-plane,passing through the right-eye reflecting mirror optical axis strikepoint, and an η-axis is defined as an axial line on the reflectingmirror which is orthogonal to the ζ-axis, passing through the right-eyereflecting mirror optical axis strike point,

in this case, a plane mirror included in the right-eye image displaydevice is rotated about the ζ-axis by an angle of θ₁ of 45 degrees±5degrees with a top of the plane mirror being rotated in a direction awayfrom the observer, and is rotated about the η-axis by an angle θ₂ of 7degrees to 21 degrees with a right end of the plane mirror being rotatedin a direction away from the observer, and

the image formation device and optical system of the left-eye imagedisplay device, and the image formation device and optical system of theright-eye image display device, are mirror-symmetrical about a virtualsurface which is parallel to a yz-plane, passing through the midpoint ofa line segment connecting both eyeballs of the observer.

[C04]

The display apparatus according to [C03], wherein the image formationdevice is located above the reflecting mirror.

[D01]

The display apparatus according to any one of [A01] to [C04], whereinthe image display device further includes a support member configured tosupport the image formation device, and

the support member configured to support the image formation device hasa support surface which is curved in an X-direction, or in aY-direction, or in the X-direction and the Y-direction, whereby theimage formation device is curved.

[D02]

The display apparatus according to [D01], wherein

a degree of a curve in the X-direction of the support surface of thesupport member is greater than a degree of a curve in the Y-direction ofthe support surface of the support member.

[D03]

The display apparatus according to [D01] or [D02], wherein

the support member includes a pressing member,

the image formation device has a rectangular outer shape, and

the image formation device has an outer peripheral portion extending inthe X-direction and fixed to the support member by the pressing member.

[D04]

The display apparatus according to [D01] or [D02], wherein

the image formation device has a rectangular outer shape, and

the image formation device has an outer peripheral portion extending inthe X-direction and held by the support member.

[D05]

The display apparatus according to any one of [B01] to [D04], wherein

the image display device includes animage-formation-device-and-reflecting-mirror-distance adjustment deviceconfigured to adjust a distance between the image formation device andthe reflecting mirror.

[D06]

The display apparatus according to [D05], further including:

a display control device configured to control a size of an entire imagefrom the image formation device, depending on the distance between theimage formation device and the reflecting mirror.

[D07]

The display apparatus according to any one of [B01] to [D06], wherein

the image display device includes an eyeball-and-lens-group-distanceadjustment device configured to adjust a distance between the lens groupand the eyeball of the observer.

[D08]

The display apparatus according to any one of [B01] to [D07], whereinthe image display device further includes a rotation device configuredto rotate the image formation device about at least one of an X-axis, aY-axis, and a Z-axis, where the X-axis is defined as an axis which isparallel to the X-direction, passing through a predetermined point ofthe image formation device, and the Y-axis is defined as an axis whichis parallel to the Y-direction, passing through a predetermined point ofthe image formation device.

[D09]

The display apparatus according to any one of [B01] to [D08], furtherincluding:

a movement device configured to move the image formation device in theX-direction with respect to the reflecting mirror.

[D10]

The display apparatus according to any one of [B01] to [D09], furtherincluding:

a left-eye image display device and a right-eye image display deviceattached to the frame, and

an inter-image-display-device-distance adjustment device configured toadjust a distance between the left-eye image display device and theright-eye image display device.

[E01]

The display apparatus according to any one of [B01] to [D10], wherein

the image formation device has a rectangular outer shape, and

wiring extends to outside from an outer peripheral portion extending inthe Y-direction of the image formation device.

REFERENCE SIGNS LIST

-   10 observer-   11, 11L, 11R eyeball of observer-   20 frame-   21 front section-   22 side section-   22A hole section-   23A arm-   23B forehead pad-   24 nose pad section-   25 holding member-   26 base-   27A key-   27B guide groove-   27C fastening section-   30, 30R, 30L image display device-   40, 40L, 40R image formation device-   50, 50L, 50R optical system-   51, 51R, 51L reflecting mirror-   52, 52R, 52L lens group-   53R, 53L housing-   54 optical member-   60 support member-   70 inter-image-display-device-distance adjustment device-   71 base-   72 side surface located outside base-   73 feed screw mechanism-   74A, 76A pin-   75A tapped hole-   74B, 75B, 76B guide groove-   80 eyeball-and-lens-group-distance adjustment device-   82 side wall-   83 feed screw mechanism-   90 image-formation-device-and-reflecting-mirror-distance adjustment    device-   91 adjustment device base member-   92, 94 shaft-   93 bushing-   95 feed screw mechanism-   96 latch mechanism-   97 pin engaging latch mechanism

The invention claimed is:
 1. An image display device, comprising: animage formation device; and an optical system configured to bring afirst image from the image formation device to an eyeball of anobserver, wherein0 (degrees)≤ω₂<ω₁≤25 (degrees) is satisfied where animage-formation-device first strike point is a point where an extendedline of an optical axis of the optical system intersects with an imageexit surface of the image formation device, a first normal line is anormal line to the image exit surface of the image formation device andpasses through the image-formation-device first strike point, animage-formation-device second strike point is a point where an extendedline of a pupil center line of the eyeball of the observer intersectswith the image exit surface of the image formation device, a secondnormal line is a normal line to the image exit surface of the imageformation device and passes through the image-formation-device secondstrike point, and ω₁ represents an angle between the extended line ofthe optical axis of the optical system and the first normal line, and ω₂represents an angle between the extended line of the pupil center lineof the eyeball of the observer and the second normal line.
 2. The imagedisplay device according to claim 1, wherein0 (degrees)≤ω₂≤1 (degrees) is satisfied.
 3. The image display deviceaccording to claim 2, wherein 0<ω₃<29 (degrees) is satisfied where ω₃represents an angle between a second image projected onto a horizontalsurface of the optical axis of the optical system and a third imageprojected onto a horizontal surface of the pupil center line of theeyeball of the observer.
 4. The image display device according to claim1, further comprising: a reflecting mirror configured to reflect thefirst image from the image formation device, wherein the optical systemis between the eyeball of the observer and the reflecting mirror, andincludes a lens group through which the image, reflected by thereflecting mirror, enters the optical system, and an optical axis of thelens group corresponds to the optical axis of the optical system.
 5. Theimage display device according to claim 4, further comprising: anoptical member between the reflecting mirror and the lens group, whereinthe optical member has a freeform surface.
 6. The image display deviceaccording to claim 5, wherein a thickness of the optical member is alonga light transmission direction and the thickness of the optical memberchanges in a horizontal direction from the observer toward the opticalmember.
 7. The image display device according to claim 6, wherein thefreeform surface of the optical member has an odd-order curved surfacein the horizontal direction.
 8. The image display device according toclaim 4, wherein the reflecting mirror has a freeform surface.
 9. Theimage display device according to claim 4, wherein the reflecting mirrorhas a concave surface.
 10. The image display device according to claim4, wherein a point where the optical axis of the optical systemintersects with a surface of the lens group facing the observer, isoutside of the pupil center line of the eyeball of the observer.
 11. Adisplay apparatus, comprising: a frame; and an image display deviceattached to the frame, wherein: the image display device includes: animage formation device; and an optical system configured to bring animage from the image formation device to an eyeball of an observer, and0 (degrees)≤ω₂<ω₁≤25 (degrees) is satisfied where animage-formation-device first strike point is a point where an extendedline of an optical axis of the optical system intersects with an imageexit surface of the image formation device, a first normal line is anormal line to the image exit surface of the image formation device andpasses through the image-formation-device first strike point, animage-formation-device second strike point is defined as a point wherean extended line of a pupil center line of the eyeball of the observerintersects with the image exit surface of the image formation device, asecond normal line is a normal line to the image exit surface of theimage formation device and passes through the image-formation-devicesecond strike point, and ω₁ represents an angle between the extendedline of the optical axis of the optical system and the first normalline, and ω₂ represents an angle between the extended line of the pupilcenter line of the eyeball of the observer and the second normal line.